1. Field of the Invention
The invention relates to an organic light-emitting device (OLED) and in particular to an organic light-emitting device with a micro-cavity structure.
2. Description of the Related Art
Organic light emitting diode (OLED) devices are useful in a variety of applications such as watches, telephones, notebook computers, pagers, cell phones, calculators and the like. Each OLED structure typically comprises an anode, a cathode and an organic emission layer interposed therebetween. When an electrical potential is present across the electrodes, holes and electrons are injected into the organic emission layer from the anode and the cathode, respectively. Light emission results from hole-electron recombination within the structure. In an active matrix type OLED device, OLED structures are classified into two types, bottom-emitting and top-emitting types.
FIG. 1 is a sectional view of a conventional top-emitting OLED structure 100. A reflective electrode 120, serving as an anode, is formed on a substrate 110. An organic emission layer 130 is formed on the reflective layer 120. A transparent metal layer 140, serving as a cathode, is formed on the organic emission layer 130. Note that the metal layer 140 reflects some of the emitted light, decreasing light emission efficiency due to the microcavity effect. In the micro-cavity structure, the emitting light may induce constructive and destructive interferences to enhance emission at a specific wavelength. However, the light intensity and wavelength may vary when viewed at various angles, such that the view angle is reduced. In other words, in the OLED with a micro-cavity structure, the color of the emission may be changed (i.e. color shift) when viewed at various angles.
Thus, there exists a need for an improved OLED capable of increasing efficiency while mitigating the color shift problem.